Abstract: A water level detection system and method for automatically controlling in real time the water height in a washing machine to assure the optimum operating level. An ultrasonic transceiver generates a plurality of ultrasonic pulses and detects the corresponding echoes. A microprocessor stores a plurality of ranging signals representing the time period between the ultrasonic pulse and the detection of the corresponding echo. A set of the ranging signals forms a mathematical or graphic signature which changes as the water level rises up through the clothes in the washing machine. The microprocessor detects when a predetermined characteristics occurs in this signature and sends a signal to the standard washing machine controls to stop the flow of water.